Eco-Sign: A Load-Based Traffic Light Control System forEnvironmental Protection with Vehicular Communications

Lien-Wu ChenDepartment of Computer

Science, National Chiao-TungUniversity, Hsin-Chu, Taiwanlwchen@cs.nctu.edu.tw

Pranay SharmaDepartment of Computer

Science, National Chiao-TungUniversity, Hsin-Chu, Taiwanpranay@cs.nctu.edu.tw

Yu-Chee TsengDepartment of Computer

Science, National Chiao-TungUniversity, Hsin-Chu, Taiwanyctseng@cs.nctu.edu.tw

ABSTRACTThe Eco-Sign system is a traffic light control system forminimizing greenhouse gases emitted by idling vehicles atintersections. Eco-Sign provides the following features: (i)it can notify vehicles to turn on/off their engines based onexpected waiting time for green lights at intersections, (ii)it can dynamically adjust traffic light timing to minimizethe number of vehicles stopping at an intersection based onvehicle arrival and departure rates, and (iii) it is a fully dis-tributed system in the sense that each intersection can learnits local traffic condition and optimize its traffic sign settingto prevent congestions and thus traffic jams. Eco-Sign thusdemonstrates a new traffic light control system for environ-mental protection.

Categories and Subject Descriptors: C.2.1 [NetworkArchitecture and Design]: Network communications

General Terms: Algorithms, Design, Management

Keywords: Dynamic Traffic Light Control, EnvironmentalProtection, Ignition Control, Vehicular Communications

1. INTRODUCTIONTraffic congestion in modern cities seriously affects the

living quality and environments. Vehicles on the roads pro-duce mass air pollution that emits greenhouse gases such ascarbon dioxide, hydrocarbons, and nitrogen oxides. Idlingvehicles caused by traffic jams and red lights at intersec-tions waste a large amount of fuel and seriously pollute theair. Studies show that the ratio of man-made dioxide emis-sions from transportation systems is about 30% [1]. Effortshave been made to increase the traffic flows in urban arterialroads [2], to reduce the waiting time at intersections [3], andto navigate vehicles in congested roads [4].In this paper, we propose a load-based traffic light con-

trol system called Eco-Sign, which can help determine thetiming of engine ignition at intersections and thus minimizegreenhouse gases emitted by idling vehicles at intersections.At an intersection, a localization unit (LU) is placed on eachroad segment before the intersection to help vehicles knowwhere they are. In addition, a traffic control unit (TCU)is connected to traffic lights to control their timing. Eachvehicle equips with a vehicle unit (VU) to receive from LUthe IDs of its road segment and TCU. It then controls itsengine ignition based on the traffic light timing from TCU.

Copyright is held by the author/owner(s).SIGCOMM’11, August 15–19, 2011, Toronto, Ontario, Canada.ACM 978-1-4503-0797-0/11/08.

Figure 1: System architecture of Eco-Sign.

In Eco-Sign, a vehicle can get the intersection informationfrom the first passed LU and register itself to TCU as stop-ing at the intersection. During the registration process, thevehicle will receive the traffic light timing from TCU and itsonboard VU can automatically turn off its engine as the re-maining waiting time is larger than or equal to a predefinedtime threshold α. If the engine is turned off by VU, it will beautomatically turned on to pass the intersection at the nextgreen light as the remaining waiting time is smaller than orequal to another time threshold β. As passing the secondLU at the intersection, VU will deregister itself from TCU.According to vehicle registration and deregistration frequen-cies, TCU can estimate vehicle arrival and departure ratesto achieve dynamic traffic light control.

Eco-Sign can thus help turn on/off engines of vehicles toreduce air pollution as they are waiting at intersections. Onthe other hand, TCU can dynamically adjust the traffic lighttiming to minimize the number of vehicles stopping at anintersection based on the observed vehicle arrival and de-parture rates. It is a fully distributed system in that eachintersection can learn its local traffic condition and optimizethe traffic sign setting to prevent road congestions. Eco-Sign thus demonstrates a new traffic light control systemfor environmental protection.

2. SYSTEM DESIGNFig. 1 shows the system architecture and vehicles’ states

at different locations nearby an intersection. On the inter-section side, it consists of a LU on each road segment, whichprovides the location information to vehicles, and a TCU,which decides and transmits the traffic light timing. On thevehicle side, a VU is equipped onboard to receive the traf-fic light timing from TCU and control the engine ignitiontiming.

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Figure 2: State transition diagram of vehicles.

Figure 3: Eco-Sign hardware components.

VU consists of a network interface, an On Board Diag-nostics (OBD) interface [5], an ignition control circuit, anda microprocessor. The network interface is to communicatewith LU and TCU. The OBD interface is to capture the cur-rent vehicle status. The ignition control circuit is responsiblefor turning on/off the engine at intersections as its speed is0 (Alternatively, this can serve as a recommendation ser-vice only.). The microprocessor collects information fromall other components and issues commands to them. LUis equipped with a directional antenna and is placed at aroad segment with a certain distance from the intersection.It periodically broadcasts location beacons on a dedicatedchannel, which contain IDs of the road segment and TCU,to vehicles entering or exiting the intersection. TCU con-sists of a microprocessor and two omnidirectional antennasoperating in distinct channels, one for vehicle registrationand the other for deregistration.Fig. 2 shows the state transition diagram of vehicles. Ini-

tially, a vehicle is in state 1 (Default State). When thevehicle approaches an intersection, it will receive beaconsfrom the first passed LU and then enter state 2 (ApproachIntersection). If it passes the intersection without stopping,it will receive beacons from the second passed LU and thenswitch back to state 1. On the contrary, if it stops at theintersection due to red lights, it will enter state 3 (Regis-tration to TCU & Ignition Control), register itself to TCU,and decide if its engine should be turned off. Note that ifit stops at the intersection more than once, it will registeritself again and turn off its engine for each stop. When itexits the intersection, it will receive beacons from the sec-ond passed LU and then enter state 4 (Deregistration fromTCU). After it deregisters itself from TCU, it will go backto state 1.

3. PROTOTYPE IMPLEMENTATIONWe have developed a prototype of Eco-Sign. The micro-

processor and network interface used in VU, LU, and TCU isJennic JN5139 [6], which has a 16MIPs 32-bit RISC proces-sor, a 2.4GHz IEEE 802.15.4-compliant transceiver, 192kBof ROM, and 96kB of RAM. As shown in Fig. 3(a), LUis implemented by JN5139 development board powered byfour AA batteries. TCU is implemented by integrating twoJN5139 development boards connected with a notebook viaUSB ports, which is running on Windows XP operating sys-tem, as shown in Fig. 3(b).

Figure 4: Prototype demonstration.

VU is implemented by JN5139 development board inte-grated with the ignition control circuit, as shown in Fig. 3(c).The interfacing circuit for ignition control is using ULN2003[7] Darlington transistor arrays, which takes the signal fromJennic I/O pins and controls 12 V, 40 A automotive relays.A Y-type connector is provided to avoid cutting the originalwires inside the car. The power of VU is supplied by the 12V in-vehicle battery.

Fig. 4 shows the prototype demonstration of Eco-Sign.TCU and LU are installed at the intersection and the road-side lamppost on each direction leading to the intersection,as shown in Fig. 4(a) and Fig. 4(b), respectively. They areoperating on 3 different channels. VU is set up in MarutiSuzuki 800 [8], as shown in Fig. 4(c). On one hand, the ve-hicle is driven from each road segment of the intersection toregister/deregister itself to/from TCU. On the other hand,the traffic light timing is varied in road segments of the inter-section and the vehicle can receive the correct timing valuefrom TCU. In addition, automatic ignition control is acti-vated as the vehicle speed is 0 km/hr and the remainingwaiting time is larger than 30 seconds.

For indoor demonstration, we use a projector to simulatetraffic conditions on road segments at an intersection, asshown in Fig. 4(d). A remote control car with VU is usedto approach the intersection and trigger operations of Eco-Sign. Fig. 4(e) shows the car status including motion status,approaching side, remaining waiting time, and ignition ad-vice.

4. ACKNOWLEDGMENTSY.-C. Tseng’s research is co-sponsored by MoE ATU Plan,

by NSC grants, 97-3114-E-009-001, 97-2221-E-009-142-MY3,98-2219-E-009-019, 98-2219-E-009-005, and 99-2218-E-009-005, by ITRI, Taiwan, by III, Taiwan, by D-Link, and byIntel.

5. REFERENCES[1] eSafety Forum. ICT for Clean and Efficient Mobility. Working

Group Final Report, Nov. 2008.

[2] Y. Li, W. Wei, and S. Chen. Optimal Traffic Signal Control foran Urban Arterial Road. In 2nd Int’l Symp. on IntelligenceInformation Technology Application, pages 570-574, Dec. 2008.

[3] E. Azimirad, N. Pariz, and M.B.N. Sistani. A Novel FuzzyModel and Control of Single Intersection at Urban TrafficNetwork. IEEE Systems Journal, 4(1):107-111, Mar. 2010.

[4] V. Verroios, K. Kollias, P. K. Chrysanthis, and A. Delis.Adaptive Navigation of Vehicles in Congested Road Networks. In5th Int’l Conf. on Pervasive Services, pages 47-56, July 2008.

[5] On Board Diagnostics. http://www.obdii.com/background.html.

[6] Jennic, JN5139. http://www.jennic.com.

[7] ULN2003, High Voltage and Current Darlington Transistor Array.http://www.datasheetcatalog.org/datasheets/120/489337 DS.pdf

[8] Maruti Suzuki 800. http://www.maruti800.com/.

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